#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>


int main()
{
    //close(0);
    //close(2);
    //close(1);
    umask(0);
    //int fd = open("log.txt", O_WRONLY | O_CREAT | O_TRUNC, 0666);
    //int fd = open("log.txt", O_WRONLY | O_CREAT | O_APPEND, 0666);
    int fd = open("log.txt", O_RDONLY);
    if(fd < 0)
    {
        perror("open");
        return 1;
    }

    dup2(fd, 0); //输入重定向

    char line[64];

    while(1)
    {
        printf("> "); 
        if(fgets(line, sizeof(line), stdin) == NULL) break; //stdin->0
        printf("%s", line);
    }


    //dup2(fd, 1);

    //printf("open fd: %d\n", fd); // printf -> stdout
    //fprintf(stdout, "open fd: %d\n", fd); // printf -> stdout

    //const char *msg= "hello world";
    //write(1, msg, strlen(msg));

    //fflush(stdout);
    close(fd);
    return 0;
}
